1. Field of the Invention
This invention relates to improvements in cylinder locks of the type having dual locking mechanisms including tumblers and a side bar. More particularly this invention relates to improvements in twisting tumbler-side bar cylinder locks.
2. Prior Art
Medeco Security Locks, Inc. of Salem, Va., a wholly owned subsidiary of Hillenbrand Industries, Inc., makes and sells a twisting tumbler-side bar cylinder lock under the Medeco trademark. The Medeco cylinder lock is fully disclosed in U.S. Pat. No. Re. 30,198 reissued Jan. 29, 1980 and such disclosure is incorporated herein by reference.
In the Medeco lock the side bar which rests in a camming slot of the cylindrical shell must have its tumbler locking lugs positioned above a horizontal center line through a center of the plug since the side bar lugs or legs must be able to avoid interference with a proper bitted key when they move into the tumbler slots.
While the Medeco twisting tumbler-side bar cylinder lock has been a significant commercial success for a number of years, it, like many successful products, could be improved.
In the Medeco lock, because the side bar legs or lugs must avoid the key, they are of necessity of a small dimension in height and because the legs are asymetrical with regard to a radial line through the camming slot they will not bear the same forces in either direction. Also, if larger and symmetrically-positioned side bar legs or lugs could be used, the lock would offer more strength against forcing. However, if the side bar legs were made larger and the side bar were positioned symmetrically with regard to a horizontal line through the center of the plug, the side bar legs would intersect the key and not operate properly, thus rendering the lock inoperative.